Let the first number be x, and the second number be y. We're given two equations:

- x = y + 15
- x + y = 51

(y + 15) + y = 51

Combine like terms:

2y + 15 = 51

Plug this equation into the search engine and we get:

**y = 18**

Now plug this into (1) to get:

x = 18 + 15

**x = 33**